DE102004062511A1 - Formation and coating of substrate in a form tool, comprises forming the substrate in a cavity of the form tool, introducing the substrate into a another cavity of the form tool and coating the substrate with a lacquer in the cavity - Google Patents

Abstract

The substrate coating is carried out using reaction injection molding, spraying or pressing under high pressure (10 bar) and hardening the substrate by precipitation. The lacquer is radical, ionic, polyaddition or hardened system, solvent-poor lacquer (solvent content 1 wt% and work life 2 minutes), solvent-free lacquer, aliphatic polyurethane or polyurea. A single/two component lacquer is injected into the substrate. The : An INDEPENTDENT CLAIM is also included for forming tool.

Description

The The invention relates to a method for molding and coating a Substrate in a mold.

Out EP 197 496 A For example, a method of molding and coating a substrate in a mold is known. The substrate is formed between two separable molds with an intermediate mold cavity until the substrate is partially cured. When the substrate is cured to the extent that its surface has formed a skin which is receptive to the coating, the coating is injected into the mold cavity. Injection of the coating occurs at a pressure substantially above the mold cavity pressure prevailing immediately prior to injection. The dies are held in a closed, pressurized position during injection without substantial retraction of the dies. The coating is thereby forced and compressed substantially over the entire surface of the substrate. According to EP 197 496 A the substrate is formed by injection compression molding EP 197 496 A Various disadvantages, such as lengthening the cycle time, should be avoided, which are associated with opening and closing of the mold prior to injection of the coating. By injecting the coating under a pressure greater than the curing pressure, according to EP 197 496 A the opening and closing are bypassed. Disadvantages to the in EP 197 496 A described method result from the fact that substrate production and substrate coating take place sequentially in a cavity. Therefore, various process parameters for the two process steps, such as wall thickness of the coating or mold surface temperature, not freely selectable.

In DE 43 16 154 A is a method for coating an interior fitting with a crosslinkable curing resin or lacquer described. In this method, the interior fitting is position defined inserted into a mold to apply a coating in the manner of an injection molding or die-casting on the surface of the interior fitting. The resin or paint is applied in the required total thickness in the closed mold in a single operation. During the entire hardening time, a pressure that is constant over time is exerted on the resin, which is initially liquid and then setting in the mold, despite a shrinkage due to shrinkage. The pressure is chosen such that any air present in the liquid resin or paint is dissolved. In the method according to DE 43 16 154 A For coating a finished interior fitting is inserted into the mold. The manufacture of the interior fitting is therefore independent of its coating. During coating, the internal mold pressure is maintained despite the shrinkage by the mold of the die is retightened. The high internal mold pressure is intended to ensure that air remains dissolved during hardening and thus does not adversely affect the quality of the coating. The external production of the over-molded Innenausbauteiles is disadvantageous, since this particular increases the expenditure on equipment of the process. The production costs are thus considerably higher.

Besides, it is off EP 934 808 A discloses a method of coating in a mold, which comprises, in a first step, producing a shaped article in the form of a synthetic resin by an injection molding method, a pre-injection method or a spray-printing method. This is done by applying a clamping pressure to a mold including a fixed mold half and a movable mold half. In a second step, the clamping pressure is reduced or the fixed and movable mold half taken apart, before in a further step, a coating material between an inner surface of the mold and a surface of the molded body is injected into the mold. The clamping of the mold after the injection of the coating material is carried out under certain multi-stage variable clamping pressures with certain Klemmdruckübergangszeitspannen. Both steps of the method according to EP 934 808 A , The molding of the molding and the coating of the molding are carried out in a cavity, wherein the curing of the coating takes place under a special pressure profile. Since the individual steps in a cavity are also carried out in this method, the same disadvantages apply as for the method according to FIG EP 197 496 A ,

US 2003/0197307 A discloses a method for injection molding a Molding and subsequent coating with one under heat curing Paint layer. The injection molding and subsequent Coating takes place in two separate mold cavities. According to US 2003/0197307 A becomes a thermosetting composition for coating essentially no volatile Contains components, used.

Over other Procedures offer the RIM method the possibility of the components directly before the introduction into the cavity to mix. This makes the process independent of the pot life of the system. The advantage could be clearly shown in experiments. Further Advantages are the significantly reduced cleaning effort as well the increased Process reliability, as faults in the field of injection molding machine no consequential damage in the metering and mixing of the paint components cause. Furthermore, can the system immediately after production interruption with the production continue with high quality painted parts.

The The object of the present invention is to provide a method for To provide molding and coating of a substrate, which the ones mentioned above Disadvantages of the prior art does not have.

• (a) Formen eines Substrats in einer ersten Kavität eines Formwerkzeugs
• (b) Einbringen des gemäß Schritt (a) hergestellten Substrats in eine zweite Kavität des Formwerkzeugs
• (c) Beschichten des gemäß Schritt (a) hergestellten Substrats in der zweiten Kavität mit einem Lack nach dem Reaction Injection Molding Verfahren, wobei das Beschichten unter Druck erfolgt.

The invention relates to a method for forming and coating a substrate in a mold having at least two cavities, comprising the following steps:

• (a) forming a substrate in a first cavity of a mold
• (b) introducing the substrate produced according to step (a) into a second cavity of the molding tool
• (c) coating the substrate produced according to step (a) in the second cavity with a lacquer by the reaction injection molding method, wherein the coating is carried out under pressure.

The inventive method is performed in a mold having two or more cavities, so that the two process steps (a) forms and (c) coating of the substrate in different cavities. The surfaces of the wells can of the same or different materials, e.g. Glass, Ceramics, plastic, metals or alloys, be made.

The Forming the substrate in a first cavity according to step (a) may be, for example by injection molding, Injection compression molding, Pressing, reaction injection molding reaction injection molding (RIM) or foaming. As materials can all thermoplastic and thermosetting plastics, e.g. PC, PBT, PA, PE, PP, PS, ABS, ASA, SAN, PET, POM, COC, PPO, PMMA, PPS, PUR, EP, PVC and their blends are used. The substrate can be of any shape.

Preferably the forming of the substrate according to step (a) takes place after the injection molding process made of a thermoplastic material. The injection molding process is well known in the art. Becomes the substrate by injection molding made of a thermoplastic material, are all thermoplastic and thermosetting plastics, e.g. PC, PBT, PA, PE, PP, PS, ABS, ASA, SAN, PET, POM, COC, PPO, PMMA, PPS, PUR, EP, PVC and their Blends suitable.

To In accordance with step (b), the substrate is shaped into a second one cavity introduced the same mold. This is the mold open and the substrate is converted into a second cavity. The implementation of the Substrate can be prepared by known methods, such as in multicolor injection molding be applied. Typical procedures are one hand moving with turntable, insert, sliding cavity or index plate or similar methods in which the substrate is on the core remains. Remains the substrate to react on the core has This has the advantage that the position even after the transfer fit is defined. On the other hand, from the prior art, methods for converting a substrate in which the substrate, e.g. with help a handling system, taken from one cavity and another cavity is inserted. The reaction with removal of the substrate offers greater freedom of design in the coating, e.g. in the generation of a Umbug or masked areas.

According to step (c) of the method according to the invention, the substrate is coated in a second cavity of the mold with a lacquer, wherein the coating is carried out under pressure. This means that both the application and the curing of the paint is carried out under pressure. A sufficient pressure is necessary both in the injection and in the Nachdruckphase, ie during curing, the paint to avoid blistering in the paint layer. The application of the lacquer layer takes place by the lacquer being filled under pressure into the cavity between the surface of the substrate and the inner wall of the cavity, for example injected. The pressure must be so high that the cavity is filled before the pot life of the paint is reached. At the same time, the pressure prevents the formation of bubbles on the flow front of the paint. The curing of the paint is carried out under pressure. During the curing of the lacquer means in the context of the present invention, the time that is at least needed to ensure safe removal of the coated substrate without damaging the lacquer layer. This pressure must be so high that a Bla senbildung in the paint during curing is prevented. Furthermore, the pressure ensures that the volume shrinkage of the paint is compensated during curing. At the end of the curing time, the pressure in the cavity must have dropped to zero.

Of the Pressure during of the coating preferably 10 to 90 bar, more preferably 40 to 60 bar. This from the outside applied pressure can during coating, i. while injection and curing, kept constant. Alternatively, the externally applied Pressure during the coating can also be varied, the pressure being preferred in the range of 10 to 90 bar, more preferably 40 to 60 bar lies. The pressure can e.g. applied by a piston from the outside become. Alternatively, the pressure can be applied by an embossing process.

The inventive method is suitable for Layer thickness of the paint in the range of 0.01 to 3 mm.

In a preferred embodiment becomes the thermal expansion the substrate and the paint used to the pressure in the cavity during coating adjust. By choosing the tool surface temperatures and / or the Residence times in the first and / or the second cavity can be targeted a cavity pressure profile as a function of the paint formulation be generated. The temperature of the first cavity is suitable for the substrate material to be processed selected. It is preferably 40 to 80 ° C. The Residence time in the first cavity is preferably 30 to 60 seconds. In the second cavity, the paint can on the substrate under a matched to the selected materials Temperature in the range of 20 to 120 ° C injected and cured. The residence time in the second cavity is preferably at least 45 seconds, more preferably 45 seconds to 2 minutes. Because the Residence time depends on the paint formulation, the residence time can also longer be, e.g. up to 10 minutes.

While in the first cavity due to the cooling the substrate shrinkage occurs, takes place in the second cavity due the heightened Temperature thermal expansion the substrate and the paint instead. The thermal expansion can be targeted be adjusted so that they have the desired internal pressure in the second cavity reached. In the second cavity is preferably heated that half of the tool to which the Lacquer layer adjacent. The raised Temperature in the second cavity favored thus not only the curing, but also allows the cavity pressure due to the thermal expansion of varnish layer and substrate to influence targeted.

Furthermore Is it possible, In different areas of the cavities, the temperature of the tool surfaces differently adjust. This can for example be used purposefully generate local cavity pressure profiles.

These embodiment, after the internal pressure in the cavity over the thermal expansion of the substrate and the varnish is advantageous for one of the following reasons Method in which the internal pressure over the externally applied Pressure is set: First, the pressure can be evenly over the entire molding to be applied without leaving paint during the curing phase into the cavity must be pressed into it. Second, the volume shrinkage of the paint by curing be balanced locally. Finally, through targeted local different tool temperature of the pressure varies during curing become.

The Coating the substrate according to step c) carried out by the RIM method, as in the prior art known. This has the advantage that the two components of the two-component Paint system only combined immediately prior to injection into the cavity become. The paint is over one or more nozzles so in the cavity injected that the cavity between the surface of the substrate and tool inner wall Completely filled with paint becomes. For an optimal injection of the paint becomes number and location of the injection points chosen in a manner known to those skilled in the art. One Criterion for the design of the second cavity is the targeted repression the one in the cavity available air and their exhaustion over the Parting plane or ventilation channels during the Injection. Therefor can for example, calculation programs, as known from the prior art are known to be used. The gate design for the paint injection can e.g. after the for the production of RIM moldings Angular variants known from the prior art take place.

The cavity for the coating of the substrate can be designed as desired, so that the paint layer is, for example, the same thickness over the entire surface of the substrate. However, the cavity may also be shaped so that the paint layer is of different thickness in different regions of the substrate. This way you can At any point of the substrate the desired paint layer thickness can be achieved.

For the coating of the substrate according to step (c) can all for the plastic coating suitable low-solvent one-component or two-component systems that are both radically, ionic as well Curing polyaddition can. As low-solvent Paint systems are those with a solvent content of particular at most 10% by weight, preferably at most 2% by weight, particularly preferably maximum 1% by weight, considered on the paint content. Particularly preferred solventless Systems used. In particular, solvent-free polyurethane coating systems or polyurea systems, with particular preference solventless aliphatic polyurethane paint systems are used.

At the Use of two-component paint systems can be thorough mixing These components depending on pot life and equipment either in the paint injection nozzle, e.g. through a high pressure counterflow mixing head, or in the supply line by static mixer or active mixing by means of a dynamic Mixer done.

at a long pot life can be the mixing of the two components also outside the plant made and the mixture as a one-component system are processed. Here, for example, the processing time by cooling the components extended before injection and by a high mold temperature in the second cavity a short reaction time can be achieved.

Usually paint systems with a short pot life are used. Prefers are systems with a maximum pot life of 30 min, especially preferably with a maximum pot life of 10 minutes, especially preferably chosen with a pot life of a maximum of 2 minutes. For a short time Pot life is preferably a high pressure counterflow mixing head for mixing used the two components. Compared to other methods this allows the highest Productivity. Furthermore remain at the end of the process, no residues of mixed coating raw materials in the mold.

In an additional Process step may be prior to molding the substrate according to step (a) and the coating according to step (c) optionally a release agent applied to the surface of the cavities, e.g. sprayed, become. As a release agent can the means known from the prior art are used.

The inventive method can also be performed in a mold with more than two cavities. So can e.g. additional lacquer layers with possibly specific properties are applied, by applying each layer of varnish in its own cavity. Farther Is it possible, several substrates in each case one cavity in a process step according to step (a) prepare in parallel and then successively in a cavity or coat in parallel in each case in a cavity according to step (c) with lacquer.

The inventive method offers opposite the prior art several advantages. The cycle time is shorter because they are not the sum of the times of the individual process steps composed. Furthermore can Process parameters such as the mold wall temperature for the process steps (a) and (c) independently chosen from each other and thus optimally adapted to the substrate material and the paint become. This can u.a. also the cycle time can be optimized. Furthermore, the thickness of the lacquer layer at any point of the cavity can be chosen freely. Furthermore, can for the surfaces the different cavities different materials, e.g. Glass, ceramics, plastic, different metals or alloys can be chosen. Also release agents, if necessary, used specifically on the tool surfaces become. Thus, e.g. achieved a good separation of the paint from the tool surface be without the adhesion of the paint on the substrate negative influence.

One Another object of the invention is a mold for performing the inventive method, comprising at least two cavities, wherein at least one cavity with an injection molding device and a cavity connected to a RIM paint injection device.

The Injection molding facility the mold according to the invention is used to produce the substrate made of thermoplastic material by injection molding in a first cavity of the tool. Suitable injection molding facilities are those skilled in the art known from the prior art. They include a standard injection molding machine construction consisting of a plasticizing unit for substrate preparation and a closing unit, the for the travel, opening and closing movements the tool is responsible, Tempiergeräte and possibly drying equipment for the substrate.

The RIM paint injection device, which in the mold according to the invention with a second cavity is connected, is used to coat the substrate with a paint according to step (C). Suitable paint injection devices are the expert from known in the art. They include one or more than one reservoir for the individual components, stirrer, Feed pumps, Tempering devices for temperature control, delivery lines and possibly one Mixing device for the mixing of more than one coating component, e.g. a mixing head for high-pressure counter-jet mixing.

The according to the inventive method prepared coated with lacquer substrates are for example suitable Automotive interior parts, such as Pillar trim, Moldings, hand-operated shed covers, covers, panels, instrument panel, Parts of the air conveyor system, and industrially manufactured plastic parts, such as e.g. Housing of Electrical appliances, Mobile phones, household items.

The invention will be explained in more detail with reference to the accompanying drawings. 1 shows on the basis of steps (A) - (H) the basic procedure. Shown is the injection mold 10 with two tool halves 11 . 12 and two cavities, a substrate cavity 13 and a paint cavity 14 , At the start (A) according to the outlined embodiment of the method according to the invention is the tool 10 closed and the core 15 is located in the substrate cavity 13 , The thermoplastic for shaping the substrate 21 is injected and solidified (step (B)). After reaching the demolding temperature, the reaction of the substrate takes place 21 from the substrate cavity 13 in the paint cavity 14 (Step (C) and (D)). This is the mold 10 opened (step (C)) and in the illustrated embodiment, the substrate molding 21 along with the core 15 in the paint cavity 14 shifted (as indicated by the arrow in step (C)). Is the substrate molding 21 in paint position (step (D)), the tool becomes 10 closed (step (E)). The paint cavity 14 ie the mold cavity between the substrate molding 21 and tool wall 16 , is with paint 22 filled via nozzles (not shown). The paint 22 is kept under pressure in the curing phase (step (F)). If the paint has reacted and is cooled, the tool becomes 10 opened (step (G)) and that with varnish 22 coated substrate 21 removed from the mold (step (H)).

Examples embodiment

A paint coated molded article having a 40 cm ² projected area was produced on an injection molding machine in a two-cavity injection mold (a substrate cavity and a paint cavity associated with a RIM unit). The molding made of thermoplastic material was a box-shaped component with oblique side surfaces. The wall thickness of the substrate molding was about 3 mm. In a series of experiments, the surfaces of the molding were provided with different paint thicknesses. The layer thickness of the paint was adjusted depending on the area in the range of about 300 to 1000 microns.

In the first step, the substrate was prepared. For this purpose, plastic granules were melted in an injection cylinder. It concerned PC + ABS blend (here Bayblend ^® T65 of the company Bayer MaterialScience AG), which was injected after the fusion process - in the same way as the standard injection molding process - into the first mold cavity of the closed mold at a temperature of 270 ° C. After expiration of the holding pressure time and cooling time of 45 s, the tool was opened. In this case, the substrate produced was held on the ejector side of the injection mold and from the substrate position ( 2 ) complete with the tool core via a slider in the paint position ( 4 ) proceed (cf. 1 ). Only the paint cavity was previously wetted with a commercial release agent of the type ACMOS 36-4566 Fa. Acmos, Germany. Thereafter, the injection mold was closed again, a closing force for a maximum pressure of 200 bar was built and a solvent-free aliphatic polyurethane paint, consisting of a solvent-free polyester polyol (Desmophen ^® VPLS 2249-1 Fa. Bayer MaterialScience AG) and a solvent-free aliphatic polyisocyanate (Desmodur ^® XP 2410 from Bayer MaterialScience AG) with a ratio of 1: 1, catalysed with about 1% DBTL, injected under a pressure of 50 bar into the paint cavity. The two paint components were conveyed by the RIM system in a high-pressure counterflow mixing head and mixed there before injection. After the end of injection, the paint injection nozzle was sealed by means of a hydraulic cylinder under a pressure of initially 50 bar to prevent backflow of the paint. As a result of the higher average mean temperature in the cavity compared to the average demolding temperature of the thermoplastic molding, the pressure in the cavity increased so much during hardening that the tool surface was very well shaped and blistering in the paint was reliably avoided. After expiry of the reaction and cooling time of 45 '', the tool was opened and the painted molded part removed from the mold. As part of the experiments, the paint injection temperature and the mold surface temperature of the paint cavity on the paint side were varied. This resulted in the following Ta belle listed pressure gradients.

As one at the pressure gradients recognizes, it came at the end of the curing time to a pressure drop on the volume shrinkage of the paint during the curing was due.

Of the Paint showed good adhesion to the substrate. The painted molding could be easily removed from the tool. The paint surface was a mirror image of the highly polished tool surface.

Comparative example

A comparative experiment was performed on a sample plate tool. Here, the tool was mounted on an injection molding machine and connected to a RIM system. The tool had a plate-shaped cavity which was filled with plastic in the standard injection molding process. After the cooling time, the paint was introduced into the still closed mold cavity. This was done via a RIM system, which mixed the two paint components by means of a static mixer in a hose system and introduced into the tool. After reacting and cooling the paint system, the tool was opened and the coated plate removed from the mold. The substrate was also a PC + ABS blend (here Bayblend ^® T65 Fa. Bayer MaterialScience AG) and the paint is a solvent celebration aliphatic polyurethane coating, consisting of a solvent-free polyester polyol (Desmophen ^® VPLS 2249-1 Fa. Bayer MaterialScience AG) and a solvent-free aliphatic polyisocyanate (Desmodur XP 2410 Fa. Bayer MaterialScience AG) with a ratio of 1: 1, catalysed with about 0.2% DBTL analogous to the example described above, but by the low catalyst concentration with much longer adjusted pot life from approx. 20 min. Shorter pot lives could not be realized in this case because of the chosen procedure and the mixing of the components in the supply line.

With This experiment was associated with the following disadvantages. Since that Mold remained closed until the paint introduction, i. between the substrate preparation and the substrate coating was not opened, had the cavity already wetted with release agent before the plastic injection process become. When injecting the plastic release agent sat down partly also on the plastic surface. This worsened the adhesion of the lacquer to the substrate is clear. Besides, could the paint thickness can not be set defined. She addressed herself after the shrinkage of the substrate and the molding geometry. This led in particular at the freely dwindling edges of the molding to a undesirable huge Paint thickness.

by virtue of the sequential implementation the process steps, the cycle time consisted of the sum of Times for the individual processes. This in turn had an impact on the election of the paint, as in this procedure, the pot life of the paint system played a significant role. The choice of the paint was thus limited.

Farther could the tool surface temperature not chosen freely so it will not be possible was, by thermal expansion the desired To achieve internal pressure profiles and the associated benefits to use.

Claims (10)

Method for molding and coating a substrate in a mold having at least two cavities comprising the following Steps: (a) forming a substrate in a first cavity of a mold (b) introducing the product prepared according to step (a) Substrate in a second cavity of the mold (c) coating the product prepared according to step (a) Substrate in the second cavity using a varnish according to the Reaction Injection Molding process, wherein the coating is carried out under pressure. Method according to claim 1, characterized in that that the shaping of the substrate according to step (a) by means of injection molding, injection compression, pressing, Foam or reaction injection molding he follows. Method according to one of claims 1 or 2, characterized that a radical, ionic or polyaddition hardening Paint system is used. Method according to one of claims 1-3, characterized that a low-solvent Paint system with a solvent content of not more than 10%, preferably not more than 2%, more preferably not more than 1 %, is used on paint content. Method according to one of claims 1-4, characterized that a solvent-free Paint system is used. Method according to one of claims 1-5, characterized in that that injected a one-component or two-component paint becomes. Method according to one of claims 1-6, characterized that a polyurethane system or a polyurea system as a paint is used. Method according to one of claims 1-7, characterized that a solvent-free, aliphatic polyurethane system is used as a lacquer. Method according to one of claims 1-8, characterized that the paint system has a pot life of a maximum of 30 minutes, preferably a maximum of 10 minutes, more preferably a maximum of 2 minutes. Mold tool for carrying out the method according to the invention, comprising at least two cavities, wherein at least one cavity with an injection molding device and a cavity connected to a RIM paint injector.